Monday, 3 August 2015

instrumentation amplifier - MCP6N11 voltage reference and output problem


I am currently trying to setup an instrumentation amplifier and I used MCP6N11. Basically I'm just trying to test the instruamp to output a certain voltage gain before I connect it to my actual circuit. I created a wheatstone bridge with an output of 2.54 and 3 volts at each leg. Therefore I have 0.46 volts difference If I input it to the intru amp. I just wanted to amplify the output at around 1 volt, therefore I need a gain of 2.


Alright, I set-up the instru amp using the standard circuit based on the datasheet of mcp6n11. I choose 5k for RF and Rg resistor which is also based on the datasheet to have a gain of 2. Now the problem is I am not getting any valid output that is near on my desired gain..I tried to conect the Vref to ground then the ouput is 0, when in Vdd the output is 5volts, when I try to connect it to a 2.5 voltage then it would just output a 2.5... I cant really figure out what is wrong, can any one help me how to properly setup the circuit, should I just leave the Vref hanging? I also tried to disconnect both Vinputs and I'm getting the same result. Here is the schematic


enter image description here


https://kg4vlw.bl3302.livefilestore.com/y2pKKagie1d4aOL-3hLpd0Dlehoh4RG8f4qeQSCCL3gAe_bgA4fLAghwMIrlpHeoxoOClvQ3Hv31gPp2NRt4BQY0swEf5RWn1JQg31ou_zbVWZ4p18dxjp1oLS5KvZl1RYYNyRUWcUSGpuvGfJUAHIz-A/schematic.png?psid=1


Note: I read some similar post like this but it wasnt confirmed if the problem was solved or how.



Thank you in advance




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